All conventional surgical operating tables are equipped with standardized side rails for the purpose of accepting various accessories which are attached to the side rail of the operating table via a socket mechanism which is free to move along the rail. Armboards are also designed which attach directly to the side rails, without the use of sockets, such armboards having their own attachment mechanisms. A conventional surgical armboard is designed to allow the board to be adjustable, but only within the plane of the surface of the operating table. The only other motion possible with such an arrangement is the actual location of the armboard along the side rail.
As armboards are most frequently employed with the patient in the supine position (face up) they have proven in this regard generally acceptable. However, when the need arises to position the patient prone (face down) to perform posterior spinal surgery, then the armboards lack sufficient adjustability to be functionally acceptable. Since the armboards are in the same plane as the top surface of the table itself, then regardless of the angle of the board to the table, with the patient face down, the shoulders will be hyperabducted, hyperextended, and posteriorly displaced. This position is quite dangerous to the patient since it may cause either a compression or a tension injury to the very large bundle of nerves passing from the neck, beneath the shoulder, and the arm called the Brachial Plexus. As the patient is anesthetized and therefore unable to react, such neurological injuries occur frequently and with a known relationship to the duration of the positional insult. A second and equally significant cause of neurological injury is the high pressure applied to the ulnar nerve at the elbow caused by the unnatural position of the upper extremity induced by the conventional armboard.